Just got a question to a good introduction or tutorial of NoSQL.
The answer is not as easy as there are not as detailed documentation as for other technologies.
Do you search for BigTable documentation or for opensource-alternatives?
A nice introduction i can remember was Ricky Ho’s NOSQL Patterns from Nov. 2009 .
Of course there is the common overview, you know yet:
– Ian Varley’s master thesis from 08/2009 
– some Cassandra slides from 2009 
– a slideshare presentation on “Key-Value stores: a practical overview” by Marc Seeger (Stuttgart 2009) 
If you prefer learn by doing, have a look on this cool Casandra tutorial of Evan Weaver from Twitter .
 Ricky Ho’s NOSQL Patterns Nov. 2009
 Varlay Master Thesis Aug. 2009
 Some Cassandra slides 2009
 Key-Value Stores – a practical overview by Marc Seeger 2009
 The Cassandra Tuturial by Evan Weaver July 2009
Hope this help.
I forget to mention this helpful tutorial on database modeling with Casandra
“WTF is a SuperColumn? An Intro to the Cassandra Data Model”  by Digg’s Arin Sarkissian.